So, here we had a serious bat infestation this past summer... over 300 in fact in our attic. We have since put up bat condos outside on our trees, caulked the house and made a "one way out" bat doors so none can return.

It got me wondering, though.

So, these bats eat bugs. I know since I was strathed a few times while they dove after their meals.

During the spring, summer and autumn there are bugs around. I don't see so many bugs (except in my house) during the winter.

What are they eating? Do they hibernate? How can they hybernate with so little body mass (I mean they are the size of MICE for Gods sake!!)? It isn't like you can stock-pile bugs like nuts and grain.

Bats hibernate, and some go south for the warmer caves. Caves will moderate the temperature. (Cave temperatures generally approximate mean annual surface temperatures, which in mid-latitudes of North America range between 50 F and 60 F.)

Storing food in the form of fat isn't that much of a problem. As you say, they have little body mass, which requires little energy when hibernating.

Your bats may be confused by the generally warm winter this year. If so, they wouldn't be the only animals, and many plants seem to be confused as well. If a real cold spell comes, look for many plants and trees to die, especially the ones that "think" they have already started their springtime.


Even in hibernation, a bat must periodically arouse to drink or urinate, or sometimes to find a cooler or warmer spot within the cave as temperatures fluctuate. Moisture from the cave walls, or the condensation on their fur, provides drinking water. A little brown bat (Myotis lucifugus), for example, may arouse at intervals of only 12 to 19 days, but also may hibernate uninterrupted for as long as 83 days, depending on temperature and other conditions. As the winter wears on, the fat a bat has stored during fall is slowly metabolized. These limited reserves must last it anywhere from five to eight months.

The amount of fat stored often depends on how far a bat must migrate--the longer the journey, the more energy required. Gray bats, with lean body weights of only about 8 grams, gain up to 8.6 grams of fat before their fall migration from Florida to northern Alabama and Tennessee. In contrast, gray bats that migrate less than 50 miles to reach the same hibernation caves store only 5.4 grams or less. - How North America's Bats Survive the Winter